Similar to this question,
Troubles with importing java package to scala project (IntelliJ 10.5.2)
how do I add a java project I have created into a scala project?
Similar to this question,
Troubles with importing java package to scala project (IntelliJ 10.5.2)
how do I add a java project I have created into a scala project?
If you selected "Scala project with SBT" sbt shares a common directory structure with maven, so if you lay things out correctly according to the way SBT / Maven expect (See http://www.scala-sbt.org/0.13/tutorial/Directories.html), then you should be able to add dependencies to the SBT file (you'll need to read up on the SBT docs), then if you do that you can just click on build.sbt and "synchronize" with the Intellij idea project to import Jar / Maven dependencies. (Or alternately you may be able to move your jars to the lib directory).
You'll just need to copy your java code to the right directories.
Hope that helps.